Search Publications
Classification of circular polarization Stokes profiles in a sunspot using k-means clustering
Mathew, Shibu K.; Raja Bayanna, A.; Louis, Rohan Eugene
The magnetic and velocity fields in sunspots are highly structured on small spatial scales which are encoded in the Stokes profiles. The Stokes profiles are in turn, derived from a sequence of polarization modulations on the incoming light that are imaged using an analyser-detector combination. Our aim is to identify Stokes profiles in a sunspot w…
A spectroscopic measurement of high velocity spray plasma from an M-class flare and coronal mass ejection
Young, Peter R.
The M1.5-class flare and associated coronal mass ejection (CME) of 16 February 2011 was observed with the Extreme ultraviolet Imaging Spectrometer on board the Hinode spacecraft. Spray plasma associated with the CME is found to exhibit a Doppler blue-shift of 850 km s-1 - one of the largest values reported from spectroscopy of the solar…
Coronal spectroscopy: Probing sources of slow solar wind in active regions, and the early phases of solar flares
Harra, Louise K.
Coronal spectroscopy has pushed forward the understanding of physical processes in all phenomena on the Sun. In this review we concentrate specifically on plasma parameters measured in sources of the slow solar wind in active regions and the early phases of solar flares. These topics are a key part of the science goals of the Solar Orbiter mission…
Uncovering the process that transports magnetic helicity to coronal mass ejection flux ropes
Pal, Sanchita
Magnetic helicity, an intrinsic property of eruptive helical flux ropes (FRs) forming coronal mass ejections (CMEs), plays an important role in determining CME geoeffectiveness. In the solar atmosphere and heliosphere, helicity remains conserved in a closed volume. Considering this fact as a basis of our study, we perform a quantitative comparison…
Flux emergence and generation of flare-productive active regions
Toriumi, Shin
Solar flares and coronal mass ejections are among the most prominent manifestations of the magnetic activity of the Sun. The strongest events of them tend to occur in active regions (ARs) that are large, complex, and dynamically evolving. However, it is not clear what the key observational features of such ARs are, and how these features are produ…
Complex network view to solar flare asymmetric activity
Taran, Somayeh; Khodakarami, Edris; Safari, Hossein
Asymmetric behavior of the solar hemispheres is an essential aspect of the activity. This paper uses a complex network approach to study the solar flare asymmetric activity in two hemispheres. We construct a network based on the locations and flare flux (GOES flux classification) from 2008 December to 2019 December for 4033 and 4725 flares on the …
Two successive partial mini-filament confined ejections
Mandrini, C. H.; Cristiani, G. D.; López Fuentes, M. +2 more
Active region (AR) NOAA 11476 produced a series of confined plasma ejections, mostly accompanied by flares of X-ray class M, from 08 to 10 May 2012. The structure and evolution of the confined ejections resemble that of EUV surges; however, their origin is associated to the destabilization and eruption of a mini-filament, which lay along the photo…
Chirality and magnetic configuration associated with two-ribbon solar flares: AR 10930 versus AR 11158
Chen, P. F.; Li, Bo; Yan, Yihua +2 more
The structural property of the magnetic field in flare-bearing solar active regions (ARs) is one of the key aspects for understanding and forecasting solar flares. In this paper, we make a comparative analysis on the chirality and magnetic configurations associated with two X-class two-ribbon flares happening in AR 10930 and AR 11158. The photosph…
The dynamic chromosphere: Pushing the boundaries of observations and models
Pereira, Tiago M. D.
The interface between the bright solar surface and the million-degree corona continues to hold the key to many unsolved problems in solar physics. Advances in instrumentation now allow us to observe the dynamic structures of the solar chromosphere down to less than 0.″1 with cadences of just a few seconds and in multiple pola…
Spectral manifestations of extremely strong magnetic fields in the sunspot umbra
Lozitsky, V. G.
Fine peculiarities of the Zeeman effect in two big sunspots of October 29, 2003, and October 25, 2014, are analyzed. In order to search spectral evidences of very strong spatially unresolved magnetic fields, the Stokes I ± V and V profiles of the Fe I 6301.5 and 6302.5 Å lines are studied in detail. Confirmed are two effects discovered earlier by …